1. Technical Field of the Invention
The present invention relates to a production process of a polyphenylene ether composition that is excellent in surface appearance of molded article, impact resistance, heat resistance, stiffness, toughness, mass productivity and production stability.
2. Related Art
For its excellent properties such as impact resistance, heat resistance, stiffness, toughness, molding processability, dimensional stability and electric properties, polyethylene ether composition has been applied to various uses such as household electrical appliances, office equipments, information equipments and automobile parts. Especially, it has been widely used for outer and inner parts of copy machines and personal computers in the field of office equipments and information equipments and various parts of peripheral devices thereof in recent years. Since high stiffness, heat resistance and dimensional stability are required, a resin composition containing an inorganic filler has been frequently used for these parts.
In general, however, it has been known that when an inorganic filler is incorporated in a resin composition, impact resistance and surface appearance of molded article are considerably deteriorated even with a small amount of the inorganic filler though stiffness and heat resistance are improved. The deterioration of these properties can be prevented by mixing a polyphenylene ether powder, an inorganic filler powder and a thermoplastic elastomer having functional group in advance and then conducting melt compounding.
On the contrary, in the case that a powder raw material is continuously fed and melt compounded in an extruder or the like for a long time, it is usually difficult to feed a large amount of powder raw material at one time to the extruder because of its high bulkiness. Further, a volatile component and water contained in the powder raw material is generated as a large amount of gas and water vapor while the material is melt compounded in the extruder, resulting in back feed of the raw material to a feeding port. Absorbing the gas or water vapor, the powder raw material forms agglomerates around the feeding port to clog it and disturb feeding of powder raw material to the extruder. As a result, extrusion of the resin becomes unstable to cause cut off of strands and make continuous extrusion operation difficult. Accordingly, polyphenylene ether resins produced according to the conventional process have not exhibited sufficient mass productivity and production stability.
As a production process of resin composition comprising a polyphenylene ether powder, there has been proposed to employ specific arrangement of powder feeding equipment and specific extrusion conditions for smooth feeding of powder raw material to an extruder to improve production stability (for example, in Patent Document 1). This process mainly focuses on improvement of mass productivity and production stability of resin composition comprising a polyphenylene ether powder, polystyrene and solid frame retardant. Therefore, it is difficult to improve mass productivity and production stability of resin composition comprising a polyphenylene ether powder and inorganic filler powder according to this process.
Further, there has been proposed a production process of resin composition wherein a specific inorganic filler and a thermoplastic elastomer are compounded into polyphenylene ether to improve impact resistance, stiffness and surface appearance of molded article (for example, in Patent Documents 2 and 3). A resin composition which is excellent in impact resistance, stiffness and surface appearance of molded article can be obtained by these production processes, but mass productivity and production stability thereof are not sufficient.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-137447    [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-263079    [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-137450